I think if you want to have sort of the equivalent situation on land it would be living in an RV on the cheap. Same basic thing - simple head with a holding tank, fiberglass keeping you out of the rain, motor, propulsion system, small living quarters, all the same stuff. It isn't totally comparing apples to apples, but it isn't apples to oranges either.
There are people who "anchor out" in RV's, that is, they spend their time "boondocking" (or "dry camping") which is essentially finding a free place to park their RV and then just living there until they either have to go find food, water, empty the holding tank, get fuel, etc, or someone tosses them off the property, or whatever. They have a lot of the same kinds of issues that people living on boats have, lot of the same equipment, same concerns, they use solar panels to keep battery banks charged up, talk about generators, all the same stuff.
So, yeah, you can get a free boat and anchor it out and never spend a penny, but you can just as easily get an old RV and live in it too. If sailing has any advantages I would think it would be these two - 1) You can move a sailboat without buying expensive fuel, and 2) It is legal to "park" your sailboat in an anchorage, whereas it is much harder to find a place to put an RV and really just stay there, eventually even Walmart is going to throw you off the lot.
You could, of course, find places to park forever if you really look, some ghost town in the middle of Nevada, but it isn't like anchoring out because you can anchor out in major metropolitan areas, and that simply isn't going to happen boondocking in an RV.
Edit - thanks Winder!